Error in Following python program

[Pramod]

#/usr/bin/python
from numpy import matrix
n=input('Enter matrix range')
fr=open('mat.txt','r')
print ('Enter elements into the matrix\n')
a=matrix([[input()for j in range(n)] for i in range(n)])
for i in range(n):
for j in range(n):
print a[j]
print '\n'

When i run the above program the following error is Coming please
Error is
Enter matrix range3
Enter elements into the matrix

1
2
3
4
5
6
7
8
9
[[1 2 3]]
Traceback (most recent call last):
File "2.py", line 10, in <module>
print a[j]
File "/usr/lib/python2.6/dist-packages/numpy/core/defmatrix.py",
line 265, in __getitem__
out = N.ndarray.__getitem__

please resolve my problem Thanks in advance
~

 

[MRAB]

#/usr/bin/python
from numpy import matrix
n=input('Enter matrix range')
fr=open('mat.txt','r')
print ('Enter elements into the matrix\n')
a=matrix([[input()for j in range(n)] for i in range(n)])
for i in range(n):
for j in range(n):
print a[j]
print '\n'

When i run the above program the following error is Coming please
Error is
Enter matrix range3
Enter elements into the matrix

1
2
3
4
5
6
7
8
9
[[1 2 3]]
Traceback (most recent call last):
File "2.py", line 10, in<module>
print a[j]
File "/usr/lib/python2.6/dist-packages/numpy/core/defmatrix.py",
line 265, in __getitem__
out = N.ndarray.__getitem__

please resolve my problem Thanks in advance
~

The matrix is 2-dimensional, which in numpy is means you need to write:

a[i, i]

not:

a[j]

and no, they're not the same!

 

[Peter Otten]

#/usr/bin/python
from numpy import matrix
n=input('Enter matrix range')
fr=open('mat.txt','r')
print ('Enter elements into the matrix\n')
a=matrix([[input()for j in range(n)] for i in range(n)])
for i in range(n):
for j in range(n):
print a[j]
print '\n'

When i run the above program the following error is Coming please
Error is
Enter matrix range3
Enter elements into the matrix

1
2
3
4
5
6
7
8
9
[[1 2 3]]
Traceback (most recent call last):
File "2.py", line 10, in <module>
print a[j]
File "/usr/lib/python2.6/dist-packages/numpy/core/defmatrix.py",
line 265, in __getitem__
out = N.ndarray.__getitem__

please resolve my problem Thanks in advance

You can either use an array instead of a matrix and continue to access the
elements like you did in your code

a = numpy.array([[1,2],[3,4]])
a[1][1]

4

or continue to use the matrix and access its elements with a tuple

b = numpy.matrix([[1,2],[3,4]])
b[1,1]

4

If you pass only one index you get another, smaller matrix:

b[1]

matrix([[3, 4]])

Once you see this printed it should be clear that b[1][1] asks for the non-
existent second row of the above matrix. Hence the error:

b[1][1]

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.6/dist-packages/numpy/core/defmatrix.py", line 265,
in __getitem__
out = N.ndarray.__getitem__(self, index)
IndexError: index out of bounds

By the way, these matrices are really strange beasts:

b[0][0] matrix([[1, 2]])
b[0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0]

matrix([[1, 2]])

Peter